|Publication number||US4525250 A|
|Application number||US 06/329,115|
|Publication date||Jun 25, 1985|
|Filing date||Dec 9, 1981|
|Priority date||Dec 19, 1980|
|Also published as||DE3048083A1, DE3048083C2, EP0054743A1, EP0054743B1|
|Publication number||06329115, 329115, US 4525250 A, US 4525250A, US-A-4525250, US4525250 A, US4525250A|
|Inventors||Ludwig Fahrmbacher-Lutz, Klaus Seidler|
|Original Assignee||Ludwig Fahrmbacher-Lutz|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (5), Non-Patent Citations (2), Referenced by (29), Classifications (27), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The invention relates to a method for the chemical removal of oxide layers from objects made of metals, in particular of titanium, titanium alloys, nickel, nickel alloys and chrome-nickel steels, so that the objects can subsequently be coated with metals, especially when the objects are immersed in an organic electrolyte medium.
Workpieces of titanium, titanium alloys, nickel, nickel alloys and chrome-nickel steel, in particular, always have an oxide layer on their surface; once it is removed by chemical or mechanical means, the oxide layer forms again spontaneously when the workpiece is exposed to air or is immersed in aqueous media.
As a result of oxide layer formation, a firmly bonded metal coating of the work piece is possible only if these oxide layers are removed before the coating operation is commenced. The subsequent coating step is effected in an organic electrolyte medium in which the workpiece is immersed. These operations including removal of the oxide layer, must be performed under absolutely oxygen- and water-vapor-free conditions in closed apparatuses, which are only exposed to argon or nitrogen gases, for example.
In order to remove oxide layers from workpieces made of the above-named metals or alloys, methods to accomplish this, which are performed in a vacuum are known e.g. where cleaning is effected by means of sputtering (German laid-open application DE-OS No. 28 09 444). A cleaning method using metal melts, which are covered with a fluxing medium, is also known (U.S. Pat. No. 2,992,135). In this latter method, especially when diffusion annealing is performed to attain improved adhesion, there may be an undesirable formation of intermetallic phases, which cause the material to become brittle (G. E. Faulkner and W. J. Lewis, "Recent Development in Ti Brazing", DMIL. Mem. (1960) No. 45, Battell Mem. Inst., Columbus, Ohio; and H. R. Ogden and F. L. Holden, "Metallography of Ti Alloys", TML Report 103, Battell Mem. Inst., Columbus, Ohio). This method is also unsuitable for manufacture of expensive, finally finished workpieces, where strict demands involving dimensional accuracy are made, because dimensional accuracy is adversely affected at the high temperatures of melting. The vacuum methods mentioned above are not only susceptible to failure but are also associated with the disadvantage of requiring very high capital investments.
It is known (E. L. White and P. D. Miller, and R. S. Peoples, "Antigalling Coatings and Lubricants of Ti", TML Report 34, Titanium Metallurgical Laboratory, Battell Institute) that a coating of a titanium substrate with aluminum causes a reduction in tool wear in thermoforming processes and also prevents heavy oxidation of the titanium. It is also known that metallic coatings on titanium surfaces improves the adhesion of lubricants thereto and thus counteracts heavy frictional wear thereof (N. Factica, "Lubrication of Ti", WDL Techn. Report 57-61 II ASTIA Doc. 155564 (1958); de F. G. A. Laat and T. Adams, "Inhibiting the Wear and Galling Characteristics of Ti", Metals Eng. Quarterly 8 (39-48) (1968); D. L. Padberg and J. J. Crosby, "Fretting-Resistant Coatings for Ti Alloys", 2nd International Conference Ti 1972, MIT, Cambridge, Mass. and E. P. Kingsbary and E. Rabinowicz, "Friction and Wear of Metals", Trans. ASME, Paper 58, Lub. 6 (1968)). Coating titanium with silver facilitates practice of a simple hard-soldering process (H. R. Ogden and F. L. Holden, "Metallography of Ti Alloys", TML Report 103, Battell Mem. Inst., Columbus, Ohio). It is further known that zinc layers, which are applied to titanium, serve to protect the substrate against contact corrosion in titanium-combination elements, which are inserted into aluminum (Metalworking Production, Zinc-Plated Titanium 104 (No. 30, P. 9, 1960)).
There is accordingly a frequent need for coating workpieces of metals, in particular those made of titanium, titanium alloys, nickel, nickel alloys, and chrome-nickel steels with a metal, particularly aluminum, zinc or silver. Especially when such coating is practiced using electrolytic means and the above-named metals and metal alloy, coating compositions, the interfering oxide layer must be removed prior to coating, while the dimensional accuracy of the workpieces is precisely adhered to.
It is accordingly the object of the invention to devise a method by which it is possible to remove the oxide layers from the surfaces of metal workpieces, in particular workpieces made of those metals and alloys named above, in an effective way without impairing the dimensional accuracy and stability of the workpieces and without impairing the physical properties of products made from workpieces, such as screws.
This object is attained by the practice of a process such as described below.
The organic media used in such process are those in which both hydrogen fluoride and alkali fluorides or ammonium fluorides are soluble. Preferably, these media are alcohols, and in particular methanol.
The treatment is preferably effected using a medium containing from 3 to 8% by weight of hydrogen fluoride, 5 to 8% by weight of ammonium fluoride and 5 to 10% by weight of an alkali fluoride, in particular sodium fluoride.
The treatment temperature is preferably between 10° C. and 50° C.
The removal of the oxide layer can preferably be electrochemically performed in accordance with the method of the invention. Specifically, the procedure is such that the workpieces are alternatively switched from an anodic to a cathodic treatment involving the addition of a conducting salt, such as sodium sulfate, and using counterelectrodes, which may be made of titanium or platinum, for example.
Following the removal of the oxide layer, the workpieces are preferably flushed with an inert solvent in an atmosphere free of water vapor and oxygen. This atmosphere is particularly an inert-gas atmosphere which is introduced under conditions free of oxygen and of water vapor, to the apparatus in which the metal coating operation is effected, preferably utilizing electrolytic means. The metal coating compositions are particularly aluminum, copper, nickel and silver; however, germanium beryllium, molybdenum, tungsten and zirconium are also possibilities. In the case of electrolytic deposition, known electrolyte systems may be made use of (U.S. Pat. No. 2,763,605; F. H. Hurley and T. P. Weir, "Electrodeposition of Al from Nonaqueous Solutions", J. Electrochem. Soc. 96, 48-56 (1949); U.S. Pat. Nos. 2,446,331, 2,446,349 and 2,446,350; Elze, Lange, Meyer, "Zur elektrolytischen Abscheidung von Al", Metall 13, 541-549 (1959); Ziegler, Lehmkul, "Zeitschrift anorg. Chem." 283, 414 (1956); R. J. Heritage, "The Electrodeposition of Al", Trans. Inst. Met. Finishing 32, 61-71 (1955); and J. H. Connor, E. E. Reid and Wood, "Electrodeposition of Magnesium and Mg. Alloys", J. Electrochem. Soc. 104, 38/41 (1957)).
The following example illustrates and explains the invention.
A workpiece, made of titanium, is secured to a suitable apparatus which assures both reliable manipulation and secure contact with electric current. The piece is then cleansed of fat residues and any other particles adhering to it using methanol in an atmosphere saturated with oxygen- and water-vapor-free inert gas, such as argon, for example.
Also in an inert gas atmosphere, the workpiece is introduced into a caustic solution comprising by weight 8% hydrogen fluoride, 5% ammonium fluoride and 10% sodium fluoride dissolved in a methanol medium. Disposed in this solution are platinum electrodes which, like the workpiece, are connected to a source of voltage. These electrodes make it possible to change the potential from +10 V to -10 V within one second. During this corroding process, a voltage ratio of the anode to the cathode of 2 to 1 is maintained, at a temperature of 15° C. The direction of the current is reversed every 10 seconds. The described process is terminated after approximately 3 minutes.
The workpiece, now cleansed and freed of any oxide layer it may have had, is subsequently flushed, again with methanol in an atmosphere saturated with an inert gas, and remaining within an inert atmosphere (argon) it is introduced into the electrolyte. In accordance with the disclosures in U.S. Pat. Nos. 2,446,331, 2,446,349 and 2,446,350, the electrolyte is an ethereous solution of 3 Mol aluminum chloride and ca. 1 Mol LiH of Li AlH; using a reversing direct current at a current density of ca. 3 A/Dm2. This electrolyte permits the deposition of smooth, dense aluminum layers of ca. 0.08 cm in thickness while attaining excellent adhesion of the coating to the foundation workpiece material.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US3468774 *||Dec 9, 1966||Sep 23, 1969||Rohr Corp||Electrolytic descaling of titanium and its alloys|
|US3562013 *||Oct 23, 1967||Feb 9, 1971||Diversey Corp||Process of deoxidizing titanium and its alloys|
|US4087367 *||Oct 20, 1975||May 2, 1978||U.S. Philips Corporation||Preferential etchant for aluminium oxide|
|US4126523 *||Apr 29, 1977||Nov 21, 1978||Alumatec, Inc.||Method and means for electrolytic precleaning of substrates and the electrodeposition of aluminum on said substrates|
|US4314876 *||Mar 17, 1980||Feb 9, 1982||The Diversey Corporation||Titanium etching solution|
|1||*||Metal Finishing Guidebook and Directory for 1978, Metals and Plastics Publications, Inc., Hackensack, N.J., pp. 128 132.|
|2||Metal Finishing Guidebook and Directory for 1978, Metals and Plastics Publications, Inc., Hackensack, N.J., pp. 128-132.|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US4618088 *||Dec 7, 1984||Oct 21, 1986||Saint Gobain Vitrage||Process for soldering a current connecting element and a current feed conductor of a heatable glass pane|
|US4755263 *||Sep 17, 1986||Jul 5, 1988||M&T Chemicals Inc.||Process of electroplating an adherent chromium electrodeposit on a chromium substrate|
|US4861407 *||Oct 16, 1987||Aug 29, 1989||The Dow Chemical Company||Method for adhesive bonding articles via pretreatment with energy beams|
|US4968383 *||Jun 8, 1989||Nov 6, 1990||The Dow Chemical Company||Method for molding over a preform|
|US5248381 *||Jun 16, 1992||Sep 28, 1993||Mtu Motoren-Und Turbinen- Union Munchen Gmbh||Etch solution and associated process for removal of protective metal layers and reaction deposits on turbine blades|
|US5376236 *||Oct 29, 1993||Dec 27, 1994||At&T Corp.||Process for etching titanium at a controllable rate|
|US5464524 *||Aug 29, 1994||Nov 7, 1995||The Furukawa Electric Co., Ltd.||Plating method for a nickel-titanium alloy member|
|US6248704||May 3, 1999||Jun 19, 2001||Ekc Technology, Inc.||Compositions for cleaning organic and plasma etched residues for semiconductors devices|
|US6355116||Mar 24, 2000||Mar 12, 2002||General Electric Company||Method for renewing diffusion coatings on superalloy substrates|
|US6416589||Feb 18, 1999||Jul 9, 2002||General Electric Company||Carbon-enhanced fluoride ion cleaning|
|US6527938||Jun 21, 2001||Mar 4, 2003||Syntheon, Llc||Method for microporous surface modification of implantable metallic medical articles|
|US6536135||Apr 11, 2002||Mar 25, 2003||General Electric Company||Carbon-enhanced fluoride ion cleaning|
|US6537816 *||Jun 14, 1999||Mar 25, 2003||General Electric Company||Standards, methods for making, and methods for using the standards in evaluation of oxide removal|
|US6800326 *||Jun 29, 2000||Oct 5, 2004||Seiko Epson Corporation||Method of treating a surface of a surface of a substrate containing titanium for an ornament|
|US6878215||May 27, 2004||Apr 12, 2005||General Electric Company||Chemical removal of a metal oxide coating from a superalloy article|
|US6913791||Mar 3, 2003||Jul 5, 2005||Com Dev Ltd.||Method of surface treating titanium-containing metals followed by plating in the same electrolyte bath and parts made in accordance therewith|
|US6932897||Mar 3, 2003||Aug 23, 2005||Com Dev Ltd.||Titanium-containing metals with adherent coatings and methods for producing same|
|US6960370||Mar 27, 2003||Nov 1, 2005||Scimed Life Systems, Inc.||Methods of forming medical devices|
|US7115171||Dec 27, 2004||Oct 3, 2006||General Electric Company||Method for removing engine deposits from turbine components and composition for use in same|
|US7611588||Nov 30, 2004||Nov 3, 2009||Ecolab Inc.||Methods and compositions for removing metal oxides|
|US7687449||Sep 20, 2006||Mar 30, 2010||General Electric Company GE Aviation||Composition for removing engine deposits from turbine components|
|US8549746 *||Jul 9, 2008||Oct 8, 2013||Valeo Schalter Und Sensoren Gmbh||Process for the surface treatment of aluminium|
|US20040173465 *||Mar 3, 2003||Sep 9, 2004||Com Dev Ltd.||Method of surface treating titanium-containing metals followed by plating in the same electrolyte bath and parts made in accordance therewith|
|US20040173466 *||Mar 3, 2003||Sep 9, 2004||Com Dev Ltd.||Titanium-containing metals with adherent coatings and methods for producing same|
|US20040188261 *||Mar 27, 2003||Sep 30, 2004||Scimed Life Systems, Inc.||Methods of forming medical devices|
|US20060112972 *||Nov 30, 2004||Jun 1, 2006||Ecolab Inc.||Methods and compositions for removing metal oxides|
|US20060137724 *||Dec 27, 2004||Jun 29, 2006||Powers John M||Method for removing engine deposits from turbie components and composition for use in same|
|US20100213793 *||Jul 9, 2008||Aug 26, 2010||Valeo Schalter Und Sensoren Gmbh||Process for the surface treatment of aluminium and a layerwise construction of an aluminium component having an electric contact|
|CN104947162A *||Jul 22, 2015||Sep 30, 2015||四川华丰企业集团有限公司||Titanium alloy surface electroplating method|
|U.S. Classification||205/212, 205/237, 252/79.4, 134/41, 427/309, 205/261, 216/101|
|International Classification||C25D5/38, C25F1/08, C25D5/34, C23G1/08, C23G1/10, C25F1/04|
|Cooperative Classification||C25D5/34, C25D5/38, C25F1/08, C23G1/10, C23G1/106, C23G1/086, C25F1/04|
|European Classification||C25D5/38, C23G1/10C, C25F1/04, C25D5/34, C23G1/08E, C25F1/08, C23G1/10|
|Dec 9, 1981||AS||Assignment|
Owner name: LUDWIG FAHRMBACHER-LUTZ, ULMER STRASSE 8, 8900 AUG
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:FAHRMBACHER-LUTZ, LUDWIG;SEIDLER, KLAUS;REEL/FRAME:003968/0117
Effective date: 19811204
|Jan 24, 1989||REMI||Maintenance fee reminder mailed|
|Jun 25, 1989||LAPS||Lapse for failure to pay maintenance fees|
|Sep 19, 1989||FP||Expired due to failure to pay maintenance fee|
Effective date: 19890625